Possible issues:
Something just went wrong within network set up
It is quite common that something could go wrong just because your machine or your router worked without rebooting for a long time. Turning it off and on again sometimes can do magic… no one in the world know why... but before trying other things, try doing the basics:
Reboot your PC
Shut down Steam and relog
Reboot your router
Check the game's file integrity
Block by your ISP
We are seeing that quite a few ISPs are blocking access to our backend service that help player to connect. We do not understand why this happens yet, but we are trying to reach out to them and try t address this. A few has already replied and unblocked us allowing players to play normally, however this process could take time.
If your ISP has any sort of app or a website where you can turn off additional security settings - try doing this, it could help!
If you know a place where your ISP shows a list of blocked sites - try looking for something that has windrose.support in it - this is us! Please unblock!
Try connecting via different connection services (even if you are from NA, if you can not connect with your friends, try selecting Asia or CIS and see if it works for you)
We cannot recommend to install any third party software, but quite a few people reported that using apps like https://one.one.one.one/ or similar to this one could help to bypass this block until it is lifted by ISPs
You network settings priorities IPv6 over IPv4
The game is currently architected to use IPv4, so if your IPv6 priority is much higher there could be connection issues. Disabling IPv6, or increasing IPv4 priority could sole that issue.
https://playwindrose.com/faq/#faq-ipv6